Power converter apparatus

ABSTRACT

A power converter and regulator combining regulating and rectifying portions into one output stage. A polyphase signal is separated into individual phases each of which is then applied to one of a number of series-regulating power transistors. The output of the transistors is summed to create a regulated DC output.

United States Patent Bulleyment [54] POWER CONVERTER APPARATUS [72]Inventor: Keith J Bulleyment, St. Paul, Minn.

[73] Assignee: Honeywell Inc., Minneapolis, Minn.

[22] Filed: Nov. 2, 1970 [2]] Appl. No.: 85,955

3,229,119 1/1966 Bohn et al ..307/299 A Feb. 15,1972

3,434,034 3/1969 Garber et al ..32l/47 X OTHER PUBLICATIONS RCATechnical Notes, RCA TN N0. 627. Aug. 1965. 32l-47 PrimaryExaminer-William M. Shoop, Jr.

Attorney-Charles J. Ungemach, Ronald T. Reiling and Gordon Reed [57]ABSTRACT A power converter and regulator combining regulating andrectifying portions into one output stage. A polyphase signal isseparated into individual phases each of which is then applied to one ofa number of series-regulating power transistors. The output of thetransistors is summed to create a regulated DC output.

12 Claims, 4 Drawing Figures PATENIEUFEB 15 m2 3.643.150

INVENTOR. KEITH J. BULLEYMENT ATTORNEY The use of separate stages toachieve the functions of ACDC conversion and regulation has beentypicalof prior art devices. A common example of such a configurationconsists of adiode'bridge used to provide full wave rectificationfollowed by a series type regulator in which a zener diode-controlledpower transistor' is used to establish aregulated DC voltage. Such aconfiguration is disclosed at page 227, Figure 16.1, of General ElectricTransistor Manual, sixth edition. The

disadvantage of such circuits with separate stages for rectification andregulation is that increased dissipation occurs-in the supply when it isused in a high current, low voltage, DC application. The reason suchsupplies have higher dissipation is that during the conduction period ofthe power transistor the current flowing to theload dissipates powerin'the forward biased diodes of the bridge andthe power transistorjunctions. As will be shortly explained, the applicant's inventioneliminates one of these sources of power dissipation.

, A further advantage of applicantscombined'converter and regulatorcircuit is its freedom from noise generation. Switching regulators arefrequently used in high current, lowvoltage applications but generateconsiderable noise in operation. Ap'plicants invention does not sufferfrom such a drawback. Finally, applicants invention provides a regulatedoutput which needs little or no filtering, a significant advantage overother low-voltage DC power supplies.

SUMMARY OF THE INVENTION An AC to DC power converter including means ofdelivering a number of AC signals of different phases each to separateterminals is connected to power transistors which receive AC signals. Ameans for providing current to the bases of the power transistors isapplied to each of these power transistors to regulate their currentoutput- Means are provided for summing the output signals of each of thepower transistors when phase-separated AC signals are applied to them.An output terminal receives the summed DC signals provided.

BRIEF DESCRIPTION OF THE DRAWING The nature of the invention anddistinguishing features and advantages thereof will be more clearlyunderstood from the following detailed description and accompanyingdrawing in which:

FIG. 1 is a circuit diagram showing a preferred embodiment of theapplicants invention to be used with six-phase input power;

FIG. 2A is a sketch showing the response of one of the power transistorsshown in FIG. 1 to a single phase AC input;

FIG. 2B is a sketch showing the summed output of a sixphase embodimentof applicants invention; and

FIG. 3 is an alternative embodiment of applicatns invention using adifferent source of base current and is adapted for use with athree-phase secondary coupled to the power transistor stage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the embodimentof applicants invention in FIG. 1, means for delivering a plurality ofphaseseparated AC signals, which may be a polyphase transformer, isshown. The polyphase transformer 10 has a Y-connected primary withprimary coils l2, l4, and 16. These primary coils receive a three-phaseinput signal, which each phase of the input 120 separated from the othertwo. For example, the

signal on coil l2may lead that on coil l4by I20", while lagging the.signal on coil 16 by 120". Polyphase transformer 10 has six secondarycoils 20, 22, 24', 26, 28 and 30. Dotted lines are used in FIG. ljtorepresent the couplingbetween primary coil 12 and secondary coils 20 and'22, between primary coil.l4 and secondary coils 24 and 26, and betweenprimary coil 16 and secondarycoils 28 and 30. The secondary coil 20,

of primary leg 12 derives an inphase signal from leg 12, while secondarycoil 22 generates a signal 180 out of phase. Similarly, the secondarycoils 24 and 26 derive their voltages from primary coil 14 and are 180out of phase. Finally, secondary coils 28-and-30 derive their voltagefrom primary coil 16, coils 28 having-a signal in phase with the primarysignal and coil'30havinga signal 180 out of phase with that of coils 28and 16. One side of each-of the secondary coils 20, 22, 24, 26, 28*and30of the polyphase transformer 10 is connected to a ground 32. The otherend of each of the secondary coils is connected to one of a plurality ofpower transistors 34, 36, 38, 40, 42, and 44 at the emitter terminal ofeach transistor. Although the embodiment of FIG. 1 utilizes six powertransistors 34, 36, 38, 40, 42 and44 a six emitter power transistorwould work equally well. If a three-phase sinusoidal input signalappears at the primary of polyphase transformer 10, six output signalswith 60phase-separation will appear, one each at the emitters of powertransistors 34, 36, 38,40, 42 and 44.

The collectors of the power transistors 34, 36, 38, 40, 42 and 44 areconnected'in common to point 50 which sums their signalsand presents thesummed current at an'output terminal 54. The output terminal 54 isprovided for the attachment of a lead impedance 'such' as theimpedance58 shown. Connected to common point 50 is a voltage divider resistor 62,which monitors the voltage at common point 50, and is adjusted toexhibit a voltage 'drop indicative of the voltage level at outputterminal 54. The voltage divider resistor 62 is connected todifferential amplifier 70 at a controlled voltage input 66, and providesan input signal thereto.

The differential amplifier 70 functions to provide a control voltage atan output terminal 80, which control voltage is dependent upon thedifference between the controlled voltage level at terminal 66 and areference voltage level established within the amplifier. A source ofpositive potential 72 is connected to amplifier 70 and provides theamplifier with operating power. Typical of the differential amplifierswhich may be successfully used as amplifier 70 in this embodiment ofapplicants invention is the LM-IOO voltage regular manufactured byNational Semiconductor. The output terminal is connected to the base ofa current driver transistor 88 through a zener diode 84. The zener diode84 provides a constant voltage drop to match the voltage levels atterminal 80 and the current driver transistor 88.

The emitter of the current driver transistor 88 is clamped to ground 32.A resistor 90 is connected between the anode of zener 84 and the base oftransistor 88 to maintain the bias of the base-emitter junction. Thecollector of current driver transistor 88 is connected to a common point92 to which the bases of the power transistors 34, 36, 38, 40, 42 and 44are connected in common. A diode 96 and resistor 100 are connected inseries between the collector of current driver transistor 88 and commonpoint 92.

A transistor 104 has its emitter connected to common point 92 and itsbase-emitter junction connected in parallel with diode 96. Transistor104 provides a source of'base leakage current for the power transistors34, 36, 38, 40, 42 and 44 during the portion of each cycle when thesebase-emitter junctions are reversed biased. This transistor is biased bythe source 72 of positive potential, and has its collector connected tosource 72 through a resistor 108. In addition, the base of transistor104 is connected to source 72 of positive potential through a resistor112.

In operation, an AC signal is applied to leads A, B, and C of theY-connected primary of polyphase transformer 10. This produces threesingle phase AC signals at coils 12, 14, and I6 respectively, eachsignal being 120 out of phase with each of the two other signals. Eachof the primary coils I2, 14, and .16 provides one inphase and oneout-of-phase signal to its secondary coils. Thus the signals at coils 20and 22 are [80 separated in phase, Similarly, the signals appearing atcoils 24 and 26, and those appearing at coils 28 and 30 are phaseseparated by 180. The result is that each of the six signals appearin gat the secondary coils of polyphase transformer 10 are phase-separatedby 60. Control amplifier 70, in conjunction with the source of positivepotential 72, provides a source of control potential at its outputterminal 80. This control potential is used to bias current driver 88,which provides current gain to the common point 92. Therefore, a sourceof regulating current is continually available at the base of each ofthe six power transistors.

Consider now the response of one of the power transistors, for example,power transistor 34, to the single phase AC input at its emitter.Suppose that a voltage V is desired at the output terminal 54. Referringto FIG. 2A, an input waveform 116 representative of the signal appearingat one of the secondary coils of polyphase transformer 10, e.g.,secondary coil 20, is shown as a dashed line trace. Solid line trace 120represents the output response of a power transistor, e.g., transistor34, to the dashed line waveform 116. When the input voltage fromsecondary coil 20 is initially zero, the emitter-base junction oftransistor 34 is reverse biased as is its collector-base junction. Atthis point, the only current flowing through transistor 34 isattributable to leakage through these junctions and the voltage at thecollector of power transistor 34 will be approximately equal to thevoltage at the emitter. As the sinusoidal voltage begins to rise, theemitter and collector voltage remain essentially coupled to one anotherbecause the transistor is fully turned why the control signal providedfrom amplifier 70, until the voltage being provided by secondary coil 20exceeds the level V V At that point, the regulator action controls theconduction of transistor 34 such that excess supply voltage appears asan increase in emitter-collector voltage for transistor 34.

The regulator, in conjunction with transistor 88, maintains theconduction of transistor 34 throughout the period 'where the appliedvoltage exceeds V Thus, regulated DC voltage appears at V for a minimumof 60 of the line voltage cycle.

Referring now to FIG. 28, six sinusoidal signals separated in phase by60 are shown. These represent the signals at the six secondary coilsshown in FIG. 1. At least one of the sinusoidal signals is at everyinstant equal to or greater than a certain voltage level V called thecommutation voltage. Therefore, if in a particular application V V ischosen smaller than V the summed output of the power transistors willsupply load current and maintain V at the desired level. Although shownfor the case of a six-phase secondary, the supply may operate with asfew as three phases of input but will naturally have greater powerlosses. In this manner, continuous voltage of a predetermined level maybe maintained at output terminal 54.

For proper operation, it is important that the base-emitter junction ofthe power transistors be able to withstand a back voltage equal to V,,,the reverse peak voltage applied by the secondary coil. The transistor104 is used to supply the leakage current to the bases of those fivetransistors which are not in conduction at any point in time. The diode96 in FIG. 1 reverse biases the emitter-base junction of transistor 104to reduce the current drive requirement for transistor 88 for maximumcontrol current situations.

The power converter apparatus thus provides AC to DC conversion andregulation without the use of a separate rectifying stage and its powerdissipation is inherently lower than that of supplies with separaterectification and regulation stages as a result. Furthermore, since noswitching regulator techniques are employed to achieve the regulation,generation of unwanted noise is minimized.

In one successful embodiment of the applicant's invention a 'volt,lO-amp DC power supply was constructed. The differential amplifier usedwas an LM-IOO amplifier built by National Semiconductor. The powertransistors used were chosen to withstand the reverse voltage V,-imposed during each cycle by the secondary coils.

FIG. 3 illustrates an alternative embodiment of the applicants inventionin which a three-phase input is utilized and output voltage regulationis provided in a different manner. A polyphase transformer havingY-connected primary coils 134, 136, and 138 is adapted to receive apolyphase input signal. The polyphase transformer 130 has secondarycoils 142, 144, and 146, each of which has one end connected to a groundterminal 150. It should be noted that any means of supplyingphase-separated AC signals to the power transistors can be used andpolyphase transformers of the Y-connected variety are not essential. Theopposite ends of the secondary coils are connected to the collectors ofthree NPN-power transistors 156, 158 and 160; the emitters of which areconnected in common to output terminal 164. Base current for each ofthese transistors is provided by secondary transistors I70, 174, and 178the bases of which are connected to diodes 180, 182, and 184. Each ofthese diodes in turn is connected to a single zener diode which has itsopposite end grounded. Additionally, the bases of the transistors 170,174 and 178 are connected through three references biasing resistors192, 194 and 196 to a source of positive potential 200. A second sourceof positive potential is connected to terminal 206 to provide power tothe collectors of the secondary transistors 170, 174 and 178.

The embodiment of FIG. 3 operates in a manner somewhat similar to thatof FIG. 1, with three major exceptions. First, a reference potential tothe bases of power transistors I56, 158 and 160 is provided by thesource of positive potential 200 in combination with the referencebiasing resistors 192, I94 and 196; diodes 180, 182 and 184; and thezener diode 190. The zener diode voltage plus the forward drop of onediode is chosen such that this reference potential is equal to thevoltage desired at the output of the power converter apparatus plus thebase-emitter voltages for the secondary and power transistors. Second,the voltage at output terminal 164 is maintained by controlling thevoltage at the base of the transistors with the zener diode, rather thanwith a current gain method as in FIG. 1. Third, in embodiments where thesecondary coils are connected to power transistor collectors, as shownin FIG. 3, the negative excursions of the input voltages from thesecondary coils 142, I44, and 146 will result in negative voltages atthe bases of the power transistors 156, 158 and 160. This means that thezener diode will no longer control the voltage at the input to thesetransistors and current will be drawn from source of positive potential200 through the coils to ground 150. In this situation, the diodes 180,182 and 184 prevent disturbing the reference voltage for the conductingstage.

While the power converter has only been described for the cases ofsix-phase and three-phase power, it will be understood that theinvention is applicable to any input of three or more phases since atleast three are necessary for a commutation point greater than zero toexist. Furthermore, although two configurations for positive DC powersupply are shown in FIGS. 1 and 3 it will be clear that by choosing PNPrather than NPN-transistors and interchanging appropriate connections,negative DC supplies could be constructed without departing from thebasic idea of the applicants invention. Finally, the source of referencepotential applied to the bases of the power transistors is not criticaland among other things, either a feedback loop with a control amplifieror a zener diode OR-connected to the three power transistor bases asshown in FIG. 3 may be used.

It will be apparent to those skilled in the art that by increasing thenumber of phase-separated AC signals a more efficient use of the powerinput may be made, since a higher voltage output and a greaterproportion of the AC waveform may be used to supply the output.

While the invention has been described and illustrated in some detail,it is to be understood that modifications may be made without departingfrom the spirit and scope of the invention as delineated by the claims.

What is claimed is:

l. A for converting AC voltage to smooth regulated DC voltage ofpredetermined amplitude, comprising in combination:

transistor means having a plurality of input terminals, a

base, and an output terminal;

means connected to the plurality of input terminals for delivering aplurality of overlapping phase separated pulses to the input terminalsthe nature of said pulses being such that the envelope of the pulsetrain at all times exceeds said predetermined voltage amplitude;

means for biasing said transistor means such that it operates in linearmode at all times during a complete supply cycle; and

control means connected to said base, for controlling current to saidbase in response to output voltage in a way to limit the voltage at theoutput terminal of said transistor means to said predeterminedamplitude, whereby presentation of a series of overlapping pulses at therespective input terminals of said transistor means results in a smoothDC output voltage signal at said output terminal.

2. Apparatus according to claim 1, wherein said means for deliveringpulses includes a polyphase transformer.

3. Apparatus according to claim 1 wherein said means for deliveringpulses includes a polyphase transformer for accepting polyphase inputsignal and producing at a first plurality of terminals a voltage whichis in phase with said input signals and for producing at a secondplurality of terminals a voltage which is X out of phase with said inputsignals; and

means for connecting each of said first and second plurality ofterminals to one of said input terminals of said transistor means.

4. Apparatus according to claim 3, wherein said polyphase transformer isa three-phase transformer producing voltage signals at six terminals.said voltage signals being overlapping half-sine waves separated inphase from each other by 60.

5. Apparatus according to claim 3, wherein said polyphase transformer isadapted for accepting an n-phase input signal and producing at 2n numberof terminals overlapping voltage signals separated in phase by 360/2ndegrees.

6. Apparatus as defined by claim 1 wherein said transistor meanscomprise a plurality of transistors.

7. Apparatus as defined by claim I wherein said transistor meanscomprises a multi-emitter transistor.

8. Apparatus as defined by claim I wherein the control means connectedto said base include a current driver, and a feedback leg is provided tosense the voltage present at said output terminal and to provide anindication thereof for com parison with a reference potential.

9. Apparatus as defined by claim 1 wherein the control means connectedto said base include a zener diode and a DC power source connected tothe zener diode.

10. Apparatus as defined by claim 8 wherein said input terminals areemitter leads.

11. The apparatus as defined in claim 10, wherein said control meansinclude a differential amplifier, connected to receive the indicationfrom said feedback leg.

12. The apparatus of claim 1 wherein said control means include anOR-connected zener diode.

3, 643,150 Dated February 15, 1972 Patent No.

- Inventor(s) Keith J. Bullevment It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 5, line 6, before for delete -A- and substitute "Apparatus.

Signed and sealed this 18th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: I9890-365-334 FORM PO-105O (10-69) mime e'm'rrs PATENT errrer @EMMQATE @F@QRREQTWN Patent NO- s, 643, 150 Dated February 15, 1972 Inventor(S)Keith J. Bullevment It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 5, line 6, before for delete -A and substitute "Apparatus",

(SEAL) Attest:

EDWARD MQDFLETGHER JRD Attesting Officer ROBERT GOTTSGHALK Commissionerof Patents USCOMM-DC 60376-P69 FORM PO-1050 (10-59) e as GOVERNMENTPRINTING OFFICE: Iss9 o-3ss-a34

1. A for converting AC voltage to smooth regulated DC voltage ofpredetermined amplitude, comprising in combination: transistor meanshaving a plurality of input terminals, a base, and an output terminal;means connected to the plurality of input terminals for delivering aplurality of overlapping phase separated pulses to the input terminalsthe nature of said pulses being such that the envelope of the pulsetrain at all times exceeds said predetermined voltage amplitude; meansfor biasing said transistor means such that it operates in linear modeat all times during a complete supply cycle; and control means connectedto said base, for controlling current to said base in response to outputvoltage in a way to limit the voltage at the output terminal of saidtransistor means to said predetermined amplitude, whereby presentationof a series of overlapping pulses at the respective input terminals ofsaid transistor means results in a smooth DC output voltage signal atsaid output terminal.
 2. Apparatus according to claim 1, wherein saidmeans for delivering pulses includes a polyphase transformer. 3.Apparatus according to claim 1 wherein said means for delivering pulsesincludes a polyphase transformer for accepting polyphase input signaland producing at a first plurality of terminals a voltage which is inphase with said input signals and for producing at a second plurality ofterminals a voltage which is 180* out of phase with said input signals;and means for connecting each of said first and second plurality ofterminals to one of said input terminals of said transistor means. 4.Apparatus according to claim 3, wherein said polyphase transformer is athree-phase transformer producing voltage signals at six terminals, saidvoltage signals being overlapPing half-sine waves separated in phasefrom each other by 60*.
 5. Apparatus according to claim 3, wherein saidpolyphase transformer is adapted for accepting an n-phase input signaland producing at 2n number of terminals overlapping voltage signalsseparated in phase by 360/2n degrees.
 6. Apparatus as defined by claim 1wherein said transistor means comprise a plurality of transistors. 7.Apparatus as defined by claim 1 wherein said transistor means comprisesa multi-emitter transistor.
 8. Apparatus as defined by claim 1 whereinthe control means connected to said base include a current driver, and afeedback leg is provided to sense the voltage present at said outputterminal and to provide an indication thereof for comparison with areference potential.
 9. Apparatus as defined by claim 1 wherein thecontrol means connected to said base include a zener diode and a DCpower source connected to the zener diode.
 10. Apparatus as defined byclaim 8 wherein said input terminals are emitter leads.
 11. Theapparatus as defined in claim 10, wherein said control means include adifferential amplifier, connected to receive the indication from saidfeedback leg.
 12. The apparatus of claim 1 wherein said control meansinclude an OR-connected zener diode.